PatchTheCVECVE-2026-62878: Stack-based buffer overflow in Windows DNS allows an unauthorized attacker to execute code over a network.
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CRITICAL 9.8REMOTEWATCHLISTUPGRADEUPGRADEMITIGATE
CVE-2026-62878 is a critical-severity flaw (CVSS 9.8) affecting windows 10 1607, windows 10 1809, windows server 2012. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.
Stack-based buffer overflow in Windows DNS allows an unauthorized attacker to execute code over a network.
Why this priority
- Critical severity
- Remotely exploitable, no login, no user action
- On your watchlist
A fixed release or distro patch exists.
Risk facts
| CVSS score | 9.8 (Critical) |
| Attack vector | Network (remote) |
| Attack complexity | Low |
| Privileges needed | None |
| User interaction | None |
| EPSS exploit chance | 1.0% (top 38%) |
| CISA exploited list | No |
| Weakness | CWE-121 |
| Published | 2026-08-11 |
| Last modified | 2026-09-02 |
Publisher (CNA): Microsoft Corporation · Vendor: microsoft
Last updated 2026-09-02 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score
Am I affected?
Timeline
- Published CVE record published
- Updated Record last modified
microsoft windows 10 1607 UPGRADE
Affected: < 10.0.14393.9418
Fixed in: 10.0.14393.9418
Safe to downgrade to: no unaffected older release
Check your OS release
cat /etc/os-release; uname -r
Debian / Ubuntu
sudo apt update && sudo apt full-upgrade
RHEL / Amazon Linux / Fedora
sudo dnf upgrade --refresh
Windows
Install the latest cumulative update from Windows Update
If no patch exists yet
OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.
microsoft windows 10 1809 UPGRADE
Affected: < 10.0.17763.9121
Fixed in: 10.0.17763.9121
Safe to downgrade to: no unaffected older release
Check your OS release
cat /etc/os-release; uname -r
Debian / Ubuntu
sudo apt update && sudo apt full-upgrade
RHEL / Amazon Linux / Fedora
sudo dnf upgrade --refresh
Windows
Install the latest cumulative update from Windows Update
If no patch exists yet
OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.
microsoft windows server 2012 MITIGATE
Affected: all versions · r2
Fixed in: no fixed release known
Safe to downgrade to: a release before r2
Check your OS release
cat /etc/os-release; uname -r
Debian / Ubuntu
sudo apt update && sudo apt full-upgrade
RHEL / Amazon Linux / Fedora
sudo dnf upgrade --refresh
Windows
Install the latest cumulative update from Windows Update
If no patch exists yet
OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.
microsoft windows server 2016 UPGRADE
Affected: < 10.0.14393.9418
Fixed in: 10.0.14393.9418
Safe to downgrade to: no unaffected older release
Check your OS release
cat /etc/os-release; uname -r
Debian / Ubuntu
sudo apt update && sudo apt full-upgrade
RHEL / Amazon Linux / Fedora
sudo dnf upgrade --refresh
Windows
Install the latest cumulative update from Windows Update
If no patch exists yet
OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.
microsoft windows server 2019 UPGRADE
Affected: < 10.0.17763.9121
Fixed in: 10.0.17763.9121
Safe to downgrade to: no unaffected older release
Check your OS release
cat /etc/os-release; uname -r
Debian / Ubuntu
sudo apt update && sudo apt full-upgrade
RHEL / Amazon Linux / Fedora
sudo dnf upgrade --refresh
Windows
Install the latest cumulative update from Windows Update
If no patch exists yet
OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.
microsoft windows server 2022 UPGRADE
Affected: < 10.0.20348.5440
Fixed in: 10.0.20348.5440
Safe to downgrade to: no unaffected older release
Check your OS release
cat /etc/os-release; uname -r
Debian / Ubuntu
sudo apt update && sudo apt full-upgrade
RHEL / Amazon Linux / Fedora
sudo dnf upgrade --refresh
Windows
Install the latest cumulative update from Windows Update
If no patch exists yet
OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.
Exact fixes by distribution
A distro patch exists: prefer upgrading over downgrading.
Fedora ELN · openbao · FIXED · 2.6.5-1.eln159 · FEDORA-2026-77adf886ae · source
sudo dnf upgrade --advisory=FEDORA-2026-77adf886ae
Fedora 46 · sugar-turtleart · FIXED · 220-16.fc46 · FEDORA-2026-b79483c788 · source
sudo dnf upgrade --advisory=FEDORA-2026-b79483c788
Install KB5120238 via Windows Update, then verify:
Get-HotFix -Id KB5120238
Windows Server 2019 (Server Core installation) · KB5120238 · FIXED · 10.0.17763.9121 · KB5120238 · source
Install KB5120238 via Windows Update, then verify:
Get-HotFix -Id KB5120238
Install KB5120242 via Windows Update, then verify:
Get-HotFix -Id KB5120242
Windows Server 2022 (Server Core installation) · KB5120242 · FIXED · 10.0.20348.5499 · KB5120242 · source
Install KB5120242 via Windows Update, then verify:
Get-HotFix -Id KB5120242
Install KB5120229 via Windows Update, then verify:
Get-HotFix -Id KB5120229
Public exploits and detection
Public code exists for this CVE. Treat unpatched systems as at risk, and only run PoCs in a lab.
- GitHub PoC: nmlz/CVE-2026-62878 (1 stars)
Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.
Quick answers
How do I fix CVE-2026-62878?
windows 10 1607: upgrade to 10.0.14393.9418; windows 10 1809: upgrade to 10.0.17763.9121; windows server 2012: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.
Is CVE-2026-62878 being exploited?
CVE-2026-62878 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.
What does CVE-2026-62878 affect?
CVE-2026-62878 affects windows 10 1607, windows 10 1809, windows server 2012. Severity is critical (CVSS 9.8). Stack-based buffer overflow in Windows DNS allows an unauthorized attacker to execute code over a network.
How urgent is CVE-2026-62878?
Priority 60/100. Critical severity; Remotely exploitable, no login, no user action; On your watchlist
Software pages
Windows vulnerabilities · Windows Server vulnerabilities
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